The present invention relates to a roller cutter adapted to be mounted to a boring head via mounting means such as a saddle. The boring head is of the type described in U.S. Pat. No. 4,274,496, which hereby is incorporated in the description, for use in reaming or full-face boring. The center line of the journal of the roller cutter is inclined an angle relative to the base surface of the saddle so that the jacket surface contacting the rock surface is essentially parallel with the base surface.
The prior art roller cutters for boring heads often exploit the fact that a diminishing cone angle on the roller cutter with an increasing distance between the roller cutter and the center of the boring head reduces wear on the roller cutter and power-requirements. The apex of the cone will then coincide with the center of the boring head so that the roller cutter achieves a true rolling movement. It is also previously known to off-set the roller cutter in the horizontal plane in order to influence the fragmentation of the rock surface. Hitherto known devices have disadvantages as they require a large number of roller cutters with different cone angles and a large number of different saddles in order to achieve a true rolling movement and off-setting according to the above-mentioned aspects. The large assortment of roller cutters and saddles required makes the risk of confusion apparent which would negatively affect the drilling operation. A large assortment is not compatible and therefore a storage problem will arise at the place of drilling. The roller cutters and the saddles are expensive and therefore a large assortment is uneconomical to keep. Furthermore it is impossible to rearrange conventional roller cutters that have been unevely worn from, for example, an outer position to an inner position on the boring head due to differences in geometry.
The object of the present invention is to solve the abovementioned problems which object is attained by giving the invention the characterizing features stated in the claims following hereinafter.